A simple and efficient protocol was developed for the syntheses of optically active epoxides（2a--2d） via the reactions of epichlorohydrin with organometallic reagents with steric hindrance at low temperature. On this basis, episulfides（3a--3d） were obtained with high e.e. values by the reaction of the corresponding epoxides with NH4SCN. The configuration of thiiranes was opposite to that of the corresponding epoxides. Then, epoxides 2a--2d were anionically polymerized and the poly-R-2a（or poly-S-2a） was proved to keep a stable one-handed helical conforma- tion in solution. The oligomers[degree of polymerization（DP）=2--5] were obtained when the thiiranes（3a, 3b and 3c） were used to polymerize.
SUN Yun-kaiZHANG JinLIU Hui-junHE LiGONG HangYANG Nian-fa
